Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine , Louisville, Kentucky 40292.
eNeuro. 2015 Dec 31;2(6). doi: 10.1523/ENEURO.0097-15.2015. eCollection 2015 Nov-Dec.
Gustatory neurons transmit chemical information from taste receptor cells, which reside in taste buds in the oral cavity, to the brain. As adult taste receptor cells are renewed at a constant rate, nerve fibers must reconnect with new taste receptor cells as they arise. Therefore, the maintenance of gustatory innervation to the taste bud is an active process. Understanding how this process is regulated is a fundamental concern of gustatory system biology. We speculated that because brain-derived neurotrophic factor (BDNF) is required for taste bud innervation during development, it might function to maintain innervation during adulthood. If so, taste buds should lose innervation when Bdnf is deleted in adult mice. To test this idea, we first removed Bdnf from all cells in adulthood using transgenic mice with inducible CreERT2 under the control of the Ubiquitin promoter. When Bdnf was removed, approximately one-half of the innervation to taste buds was lost, and taste buds became smaller because of the loss of taste bud cells. Individual taste buds varied in the amount of innervation each lost, and those that lost the most innervation also lost the most taste bud cells. We then tested the idea that that the taste bud was the source of this BDNF by reducing Bdnf levels specifically in the lingual epithelium and taste buds. Taste buds were confirmed as the source of BDNF regulating innervation. We conclude that BDNF expressed in taste receptor cells is required to maintain normal levels of innervation in adulthood.
味觉神经元将味觉感受器细胞（位于口腔中的味蕾中）传来的化学信息传递到大脑。由于成年味觉感受器细胞以恒定的速率更新，因此当新的味觉感受器细胞出现时，神经纤维必须与它们重新连接。因此，维持味蕾的味觉传入是一个活跃的过程。了解这个过程是如何调节的是味觉系统生物学的一个基本关注点。我们推测，由于脑源性神经营养因子（BDNF）在发育过程中是味觉感受器传入所必需的，它可能在成年期发挥维持传入的作用。如果是这样，那么当 Bdnf 在成年小鼠中被删除时，味蕾应该会失去传入。为了验证这个想法，我们首先使用在 Ubiquitin 启动子控制下具有诱导型 CreERT2 的转基因小鼠在成年期从所有细胞中去除 Bdnf。当 Bdnf 被去除时，大约有一半的味蕾传入被丢失，并且由于味觉感受器细胞的丢失，味蕾变小了。每个味蕾失去的传入量各不相同，失去最多传入的味蕾也失去了最多的味觉感受器细胞。然后，我们通过特异性降低舌上皮和味蕾中的 Bdnf 水平来测试味觉芽是这种 BDNF 的来源的想法。味觉芽被证实是调节传入的 BDNF 的来源。我们得出结论，表达在味觉感受器细胞中的 BDNF 是维持成年期正常传入水平所必需的。
